SEISMOLOGY AND GEOLOGY

ATTEMPT ON STUDYING TERTIARY GEOMAGNETIC EVENTS BY USING K-Ar CHRONOLOGY

LI Ji, LI Da-Meng, WANG Yu

2000, 22(s1): 2. DOI: ISSN:0253-4967.0.2000-S1-001

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By K-Ar chronology, we have preliminarily attempted on careful dating for a Tertiary volcanic profile in Zuoyun, Shanxi Province. Many times of tests indicate that the results best reappeared by using 200～280μm grade samples. Measuring 4～5 times for one sample, the error may be in 3%. After comparing K-Ar results with magnetic investigation, it can be found that it is feasible to study Tertiary geomagnetic events through K-Ar dating and terrestrial magnetism.

ADVANCEMENT OF K-Ar AND ~(40)Ar-~(39)Ar DATING FOR YOUNG VOLCANIC ROCKS

LI Da-Meng, LI Ji, WANG Yu

2000, 22(s1): 7. DOI: ISSN:0253-4967.0.2000-S1-002

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The key technique to determine the ages of young volcanic rocks by K-Ar and 40Ar- 39Ar methods is how to avoid effects of excess argon and to raise the relative component of radiogenic argon. It is possible to obtain the ages of volcanic activity in the order of tens of thousand to thousands years by distinguishing compositions with excess argon in volcanic rocks and through selecting high-K materials as measuring factors and rational gassing in the experiment processes. Examples are as follows: Usin

CHRONOLOGICAL RESEARCH OF GEOMORPHIC SURFACE ON LOWER TERRACES OF SEVERAL MAJOR RIVERS IN THE YANHUAI BASIN AND ITS ADJACENT AREAS

JI Feng-Jie, ZHENG Rong-Zhang, LI Jian-Beng, YIN Jin-Hui

2000, 22(s1): 13. DOI: ISSN:0253-4967.0.2000-S1-003

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A comprehensive study of chronology for the lower terraces along several major rivers in the Yanhuai basin and its adjacent areas is made by TL,IRSL and 14C dating as well as the Spore-pollen analysis method. The deposited ages of sediments heve been dated and the formation times of the geomorphic surfases for these lower terraces are estimated. The results show that the lower terraces in this region are associated with the regional motion and the climate conditions since late Pleistocene time

SEVERAL NOTABLE PROBLEMS ON DATING OF YOUNG VOLCANIC ROCKS BY FT METHOD—ILLUSTRATED BY DATING OF CHANGBAISHAN VOLCANIC ROCKS

MO Jing-Lin, ZHENG De-Wen

2000, 22(s1): 19. DOI: ISSN:0253-4967.0.2000-S1-004

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Based on the experience of our dating young volcanic rocks from Changbaishan and Tengchong by the fission track method, several notable problems on dating of young volcanic rocks are illustrated by dating of Changbaishang volcanic rocks. At the same time, the possible solutions to the problems are advised. We hope all these will be helpful for later research work

DETRITAL GRAIN THERMOCHRONOLOGY—&mdash|A POTENTIAL METHOD FOR RESEARCH ON COUPLING PROCESS BETWEEN BASIN AND MOUNTAIN

ZHENG De-Wen, ZHANG Pei-Shen, MO Jing-Lin, LI Da-Meng

2000, 22(s1): 25. DOI: ISSN:0253-4967.0.2000-S1-005

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The unreseted mineral grain with low closure temperature (such as zircon and aptite FT and felspar Ar-Ar dating system) located in clastic sedimentary sequence records much information about the process of mountain building and basin deposition. So it becomes a main object of detrital grain thermochronology. Detrital grain thermochronology is a promising method for recovery of basement exhumation history, for determining provenance and the maximum deposition age and for stratigraphic correlation. We first

CHARACTERS OF QUARTZ THERMOLUMINSECENCE PREDOSE AND ITS APPLICAION TO GEOLOGY

YIN Gong-Meng, LI Cheng-Hua

2000, 22(s1): 37. DOI: ISSN:0253-4967.0.2000-S1-006

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There is a thermoluminescence 110℃ peak in quartz. This peak is very sensitive to irradiation and has different sensitivity for varying heated histories. The paleodaose can be determined by the TL predose dating method of the 110℃ peak, using a small quantity of quartz. In this paper, we present the charactes of quartz TL 110℃ peak and its application to geology

REVIEW ON THERMOLUMINESCENCE DATING OF VOLCANIC ROCKS

ZHENG Rong-Zhang, JI Feng-Jie, LI Jian-Beng

2000, 22(s1): 42. DOI: ISSN:0253-4967.0.2000-S1-007

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As a bridge to join the age gap between the radiocarbon and potassium-argon, thermoluminescence (TL) dating is widely used in archaeology, geology and project surveying. Application to young volcanic rocks is a significant direction of thermoluminscence dating research. It is the special character of thermoluminescence of the measured object that makes the research and application of thermoluminescence full of bends. Based on reading documents, the common principle of volcanic rocks thermoluminescence

STUDY ON THE METALLOGENETIC TIMES OF THE CHAHANSALA Sb-Ag ORE BELT

HU Shi-Ling, MAN Fa-Qing, NI Shou-Bin, WANG Zhao-Rong

2000, 22(s1): 51. DOI: ISSN:0253-4967.0.2000-S1-008

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Using the conventional 40Ar- 39Ar age dating technique, the metallogenetic times of five meneral deposits of the Chahansala Sb-Ag ore belt in Xingjiang are systematically determened. Although all values of their ages are not identical, these metallogenetic times as a whole belong to the Yanshanian time rather than the Hercynian time, as suggested by other researchers. Furthermore, age dating results indicate that the metallogenitic epoch in middle and eastern sections of the ore belt belongs to

PALEOCLIMATIC AND PALEOMONSOONAL VARIATIONS IN CENTRAL CHINA RECORDED BY STABLE ISOTOPIC RECORDS OF STALAGMITES FROM BUDDHA CAVE,SOUTH SHAANXI

LI Gong-Chun, GU De-Long, Dorte Paulsen, WANG Fei, CHEN Wen-Ji, YIN Gong-Meng, CHENG Hai, R.L.Edwards

2000, 22(s1): 63. DOI: ISSN:0253-4967.0.2000-S1-009

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Two stalagmites were collected from Buddha Cave (109°10′E, 33°45′N), Zashui county of Shaanxi Province. The chronologies of these stalagmites were determined by lamination counting and by the 210Pb and 230Th (TIMS) methods. From the young stalagmite SF we have obtained a high-resolution δ 18O-δ 13C record spanning the past 750 years and a low-resolution record over the Holocene. The preliminary results of the old stalagmite SFL show the climatic variations between 80 ka and 330 ka. The

CHROMITE LAMELLAE IN OLIVINE OF DUNITE

CHEN Li-Hui, ZHOU Xin-Hua, CHEN Chao-Hai, ZHANG Guo-Hui

2000, 22(s1): 79. DOI: ISSN:0253-4967.0.2000-S1-010

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Chromite lamellae are found in olivines (Fo=90) of a dunite xenolith in dioritic intrusion of Laiwu, Shandong Province, East China. Metasomatic veinlets in the xenolith , mineral chemistry and a topotaxial relationship between olivine and lamellae indicate that chromite lamellae in olivine can be found in high-deformed high-Cr dunite oxidized by matasomatic fluids with lower equilibrated temperature only

FEATURES OF EXCESS OF U IN VOLCANIC ROCKS OF CHANGBAISHAN TIANCHI——THE EVIDENCE FOR SUBDUCTION OF WESTEM PACIFIC PLATE

WANG Fei, CHEN Wen-Ji, BANG Zi-Cheng

2000, 22(s1): 87. DOI: ISSN:0253-4967.0.2000-S1-011

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samples of lava and pumice from the cone of Changbaishan Tianchi Volcano, Jiling, China were measured for their uranium and thorium isotopic compositions by using the high precision U-series TIMS method. The results indicate that the U-series disequilirium system is characterized by excess of 238U (namely the radioactivity ratio of 230Th/ 238U less than 1), showing the fluids has worked in the magmatic reservoir. This may suggests that the fluids, which participated in the melting of the source r

GEOCHEMICAL CHARACTERISTICS OF RETROMETAMORPHIC ECLOGITE IN RAOBAZAI, NORTHERN DABIE MOUNTAINS

TUN Yuan-Bao, CHEN Dao-Gong, CHENG Hao, JIA Qun-Ke

2000, 22(s1): 99. DOI: ISSN:0253-4967.0.2000-S1-013

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In the eclogite from Raobazai ,Na 2O and K 2O are negative.They display MORB-normalized trace element diagrams characterized by partial LILE(Rb、Ba) positive anomalies, with no significant other elements fractionation, and without significant Nb and Ta anomalies. In the chondrite-normalized REE pattern, they show LREE depleted to slight enriched, without Eu anomaly. All of these indicate the original rocks may be oceanic tholeiitic basalt. The northern part of Northern Dabie Mountains may represent the

TIMING, LOWER BOUNDARY, GENESIS, AND DEFRORMATION OF XIYU FORMATION AROUND THE WESTERN MARGINS OF THE TARIM BASIN

CHEN Jie, YIN Jin-Hui, QU Guo-Qing, ZHANG Ke-Qi

2000, 22(s1): 104. DOI: ISSN:0253-4967.0.2000-S1-014

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Recent magnetostratigraphic and lithostratigraphic studies in the western Tarim basin have led to better constrained depositional and deformational histories. As a lithostratigraphic unit, the Xiyu Formation consists an abruptly upward-coarsening fanglomerate locally interbedded with lenticular sandstone and sandy mudstone beds. It is unconformably or disconformably overlain by the Wusu formation. The concordantly underlying Atushi Formation is predominately fluvial siltstones, sandy mudstones, and rippled

FORMATION AND DYNAMIC ANALYSIS OF NS TRENDING STRUCTURES IN SOUTHERN TIBET

WANG Yu, LI Ji, MO Jing-Lin, LI Da-Meng

2000, 22(s1): 117. DOI: ISSN:0253-4967.0.2000-S1-015

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Since the late Cenozoic (5～4Ma), whole and quick uplifting has occurred and, at the same time, widely distributed NS trending rifts or rift-depressions and NE and NW trending strike-slip faults have been developed in southern Tibet. The NS trending normal faults, NE and NW trending strike-slip faults are the major active tectonics in southern Tibet. The formation of these structures may indicate that the NS direction compression in a deep lithospheric layer has resulted in NS trending linear structures par

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